In a railway vehicle steering truck, a steering axle moves in a front-back vehicle moving direction (referred to below simply as a front-back direction) by means of a steering device when passing through a curve. However, if the steering device is broken because of some type of accident, there results an extreme reduction in the supporting rigidity in the front-back direction between the truck frame and the wheel axle. Accordingly, it is necessary to prevent the truck frame and the steering axle from separating, even if the steering device breaks, and therefore, steering trucks with a variety of structures have been disclosed in the past.
For example, in Patent Reference 1 there is disclosed a truck which has an axle box front-back suspension which is arranged in parallel with the steering device. Such a truck is able to maintain a relative positional relationship between the truck frame and the steering axle by means of the axle box front-back suspension, even if the steering device is damaged.
However, in the truck disclosed in Patent Reference 1, if the steering device is operating normally, the axle box front-back suspension requires a mechanism with a broad range of motion, because the steering axle is moved to a great extent in a front-back direction by the steering device when passing through a curve.
In Patent Reference 2, there is disclosed a truck having a steering device and an axle box front-back suspension arranged integrally or in parallel. Such a truck is able to maintain a relative positional relationship between the truck frame and the steering axle, even if the steering device is damaged.
However, the truck disclosed in Patent Reference 2 has the same problem as in Patent Reference 1, because, if the steering device is operating normally, the steering axle is moved to a great extent in a front-back direction by the steering device when passing through a curve.